Electron density analysis of the layered antiferromagnetic compound Cu2(OH)3NO3:: Relationship with the magnetic interaction mechanism

The electronic properties of the antiferromagnetic layer compound copper hydroxonitrate [Cu-2(OH)(3)NO3] are investigated by high-resolution single-crystal x-ray diffraction at 114 K. A pseudoatomic multipolar model is used to reconstruct the experimental electron density (ED) distribution, whose quantitative analysis is performed through the quantum theory of atoms in molecules. The topological properties of the ED indicate indirect Cu center dot Cu bonds mediated by the hydroxo and nitrate ions among the two-dimensional (2D) copper lattice. A mean charge transfer of 0.4 electrons from the copper atoms to the hydroxo groups and of 0.76 electrons to the nitrate ion is determined via numerical integration of the ED over the atomic basins. Low but nonetheless significant Cu-O partial covalent bonds do also exist. Interplane interaction pathways are furthermore localized and characterized.